This invention relates to an oven for preparing food products. More specifically this invention relates to an oven including two heating means which supply heat energy to a food product at two different rates. This invention furthermore relates to an oven for preparing a food product wherein one surface of the food product must be heated at a first energy input rate and wherein a second surface of the food product must be heated at a second energy input rate, the second rate being greater than the first rate.
With the popularity of fast food restaurants a variety of fast foods have become popular. The speed at which these foods are prepared is extremely important as both the restaurant operators and the diners prefer that the food be prepared in a very short amount of time so that a diner needs to wait for his food only a relatively short amount of time. However, the speed at which the food is prepared should not detract from the quality of the food. Thus, a variety of ovens have been developed which are specially suited for preparing various types of foods in a short amount of time.
Certain types of food require that the rate of heat energy input into one surface of the food product be different than the rate of heat energy input into another surface of the food product. This is particularly true with a food such as pizzas. Pizza has become a very popular fast food and a number of different types of pizzas have become popular. Pizzas normally have a crust, a filling composed of vegetables, meats, and cheeses, and a top layer of cheese onto which may be placed a variety of toppings. Thus, the top surface of the pizza requires that a limited amount of heat energy input is provided so that the cheeses will melt, and after baking will have a milky white appearance with just a small amount of brown spots thereon. At the same time the crust, or bottom surface of the pizza, must be browned. Certain pizza products which have become very popular are referred to as "deep dish" or "stuffed" pizzas. These pizzas have a much greater thickness or cross section than conventional pizzas and therefore require a greater amount of heat energy input. However, only a small amount of heat energy can be supplied through the top of a pizza since application of a large amount of heat to the top surface would cause the cheese to burn, which is, of course, undesirable. Therefore, pizza products and in particular very thick pizza products require that the rate of heat energy input into the top surface of the pizza be much lower than the rate of heat energy input into the bottom surface of the pizza. What is therefore desired for preparing pizza products in a short amount of time is an oven wherein a large amount of heat energy is applied to the bottom surfaces of the pizzas and a much smaller amount of heat energy is applied to the top surfaces of the pizzas.
A method which has been used successfully for preparing pizzas is described in U.S. Pat. No. 4,154,861. This patent discloses an impingement process wherein a conveyor belt travels through an oven cavity on which the pans containing the pizzas are located. Columns of hot air are directed at localized areas of the pizza containers to bake the pizzas and to carry away moisture and other particles resulting from the cooking process. This method has been used successfully by pizza establishments. However, if this type of oven were to be used with stuffed types of pizzas the tops of the pizzas would be burned while the crusts of the pizzas and the inside of the pizzas would not yet be properly baked.
U.S. Pat. No. 4,462,383 discloses an impingement oven for preparing foods. A pair of duct fingers is provided, each having a jet plate through which hot air is emitted in standing columns to impinge upon food products located in an oven cavity between the duct fingers. The food travels on a conveyor belt through the oven cavity between the duct fingers while it is being cooked.
It should be noted that if the temperatures in the impingement oven were to be lowered so that the top surfaces of the pizzas would not burn, the temperatures in the oven would be too low to effectively prepare the inside of the pizza products in the desired amount of time. Alternatively, if low cooking temperatures were used, the process for properly baking the pizza would be longer than desired. It is therefore desired to provide an impingement oven wherein the heat energy supplied to the bottom surface of a pizza is greater than the heat energy which is supplied to the top surface of a pizza.
Frequently, a fast food establishment will serve both thin conventional pizzas and stuffed pizzas. However, restaurant operators frequently wish to use only a single oven to prepare both thin pizzas and stuffed pizzas at the same time. Thus, an oven might have in it at same time one or more thin pizzas and one or more stuffed pizzas. It is therefore desired to provide an oven which is capable of preparing both thin conventional pizzas and stuffed pizzas at the same speed and in the same amount of time.